This invention relates to an air dryer assembly for a compressed air system, such as a compressed air braking system for commercial vehicles, and more specifically to an air dryer with a purge air cleaning cartridge.
Commercial vehicles such as trucks, buses, and large commercial vehicles are typically equipped with a compressed air braking system in which the brakes of the vehicle are actuated by compressed air. An air compressor is operated by the vehicle engine and storage reservoirs maintain a quantity of pressurized air for the brakes and other compressed air uses. Moisture and oil are two attendant problems associated with compressed air systems and are particularly problems that can adversely affect brake system operation.
As a result, an air dryer is incorporated into the compressed air system, and likewise an oil filter. The oil filter is able to remove coalesced oil while the air dryer is effective at removing moisture and oil vapor. Typically, the compressed air passes through a porous material to collect or coalesce the oil before the compressed air passes through a desiccant material that adsorbs or removes moisture from the compressed air. The desiccant material is periodically purged of its moisture content by a reverse or purge flow of air from a segregated purge volume through the desiccant material. During normal operation of these pressure swing absorption air dryers, small quantities of water and oil are expelled with the purge air upon each purge cycle. Water that condenses in the air line and is captured by the desiccant and oil present from bypass lubrication in the air compressor cylinders are expelled to atmosphere and the road surface. Oil on a road surface creates a traction hazard during wet weather and is not environmentally favorable. Likewise, since engine oil is used for compressor lubrication, the air dryer purge is an environmental release point for engine oil contaminated with heavy metals.
In known air dryer systems, the desiccant is periodically replaced. xe2x80x9cSpin-onxe2x80x9d type of canisters or cartridges are particularly desirable since they facilitate maintenance and replacement. In this manner, a desiccant canister is easily removed and substituted with a new canister.
Accordingly, a need exists for a design that addresses the discharge of oil to the environment, and still maintains the ease of maintenance and does not otherwise adversely impact on the operation of the air dryer assembly.
A method and apparatus for cleaning purge air from a compressed air system prior to discharging the air to the environment is provided. In one embodiment, the apparatus is an air dryer which includes a housing having an inlet and outlet that communicate with a cavity having a desiccant material therein. A purge reservoir operatively communicates with the desiccant material cavity for receiving a flow of air purging the desiccant material of moisture before it is introduced to atmosphere. In one embodiment, an oil absorbent cartridge is in communication with the purge valve outlet of the air dryer and includes an absorbent material for removing oil from the air purging the desiccant material.
Another aspect of the present invention is a method of collecting oil from a flow of air purging the desiccant material of an air dryer. In one embodiment, the method includes purging an air dryer with a purge air flow and separating oil from the purge air flow prior to discharging the purge air flow to atmosphere. An optional additional aspect of the method includes recycling the oil collected in the oil absorbent cartridge that is affixed to the purge valve outlet of the air dyer.